I think the straight sets have value for beginners and intermediates, as some of the work is helping to build muscle and tendon/ligament strength. But for the highly experienced/late intermediate I do have to question the value of the straight set, lower intensity approach.

Currently I am not a fan of doing sets that are not:

A) Heavy for the purpose of building strength.
B) All out, for the purpose of building muscle. (Not to failure; but rather near failure)

I spent 18-24 months stagnating on bench and squats, and tried everything you can image. Keep in mind that this stagnation was occurring in the 80-85% of 1RM range and below. I was no longer able to go from 5 to 6 reps on a lift. I tried moving squats from a 405x5 for nearly 18 months and never gained a single rep from all the various things I tried.

One thing I found out is that I was wasting a lot of work. Instead of doing intense work (90%+), I was still trying to play the simple progression game, which involved adding reps to a lower frequency set/rep structure, or adding weight to a lower frequency set/rep structure. Neither worked for me at all at this point.

I believe at some point in our training most of us simply won't add much strength knocking out set after set of 5 reps. As one gets stronger, the game changes and this simply is not the best way to challenge the body and add strength. (This excludes the training of weak areas using certain lifts, as they are probably still responding to simple progression quite well)

Certainly the game is different for everyone, but I personally feel at some point lower intensity rep-training can be a huge waste of effort.

I think the intensity has to be there as some point. Which method is most effective - Westside, 16 week periodization, whatever, is debatable. But 90%+ training has to be there at some point.

As an intermediate I never found value in doing straight sets. It was always easier, and more challenging for me to try and move from 5 reps to 8 reps with a weight, than to stick with a 3x5 or 5x5 and add weight each week.

I simply don't think weekly weight additions are the best approach once you leave the beginner stage behind. Some of the sets can be soft, meaning not challenging, and I would prefer to try and push on every set.

That's just me. I hate wasting sets. I would rather do 3 sets and push for max reps than to do a 5x5. As an intermediate I wanted to leave the gym every workout knowing I pushed progression to the limit.

All this is merely my personal experience. Mileage may vary. Please consult your physician before engaging in frequent physical activity. If an erection lasts longer than 3 hours, contact your local ER. I reserve the right to be wrong.